Base station device

ABSTRACT

A base station apparatus according to the present invention is provided with antenna elements for a plurality of branches arranged so as to have a mutually vertical positional relationship at a sequence-specific predetermined position in the horizontal plane on a sequence-by-sequence basis, a signal processing section that generates a weight specific to each above-mentioned sequence by performing adaptive array antenna processing using a signal received by an antenna element for each sequence on a branch-by-branch basis, and generates a combined signal that combines signals resulting from multiplying a signal transmitted by an antenna element for each above-mentioned sequence by a sequence-specific weight, and a diversity combining section that generates a received signal by performing diversity combining using combined signals for each branch. By this means, it is possible to suppress the effects of fading and interference and obtain a received signal with good characteristics while maintaining good communication quality in a mobile station apparatus.

TECHNICAL FIELD

[0001] The present invention relates to a base station apparatus used ina digital mobile communication system, and more particularly to a basestation apparatus provided with an adaptive array antenna.

BACKGROUND ART

[0002] A conventional base station is provided with an adaptive arrayantenna (hereinafter referred to as “AAA”) in order to suppress theeffects of interference waves (such as adjacent-channel interferencewaves, same-channel interference waves, and delayed waves) in a receivedsignal. A base station provided with an AAA has a plurality of antennas,and can strongly receive only an electromagnetic wave arriving from adesired direction (hereinafter referred to as “forming receptiondirectionality”) by providing amplitude and phase adjustment for thesignal received from each antenna (that is, each received signalsequence). Amplitude and phase adjustment for a received signal iscarried out by multiplying each received signal sequence by asequence-specific complex coefficient (reception weight).

[0003] A base station provided with such an AAA can strongly transmit anelectromagnetic wave in a desired direction (hereinafter referred to as“having transmission directionality”) by transmitting a transmit signalmultiplied by a sequence-specific complex coefficient (transmissionweight) via an antenna corresponding to a sequence.

[0004] There are two main methods, as described below, for arrangingantennas in this kind of base station. Firstly, there is a method(hereinafter referred to as “method 1”) whereby the antennas arearranged in positions such that the fading correlation between thesignals received by the antennas is virtually 1.

[0005] When method 1 is used, a base station can obtain greater arraygain both when receiving and when transmitting. For example, if thetotal number of deployed antennas is designated N, introducing an arrayantenna makes it possible to obtain a received signal that has a 2N-foldantenna gain. Also, introducing an array antenna makes it possible toobtain a received signal that has an N-fold S/N ratio.

[0006] Secondly, there is a method (hereinafter referred to as “method2”) whereby the antennas are arranged in positions such that the fadingcorrelation between the signals received by the antennas is virtually 0.

[0007] When method 2 is used, since the fading correlation between thesignals received by the antennas is virtually 0, a base station canperform diversity reception using the signals received from therespective antennas. As a result, a base station can obtain a betterreceived signal, with decreased fading effects, than when method 1 isused.

[0008] However, the following problems apply to a base station providedwith a conventional AAA such as described above. When method 1 is used,since the fading correlation between the signals received by theantennas is virtually 1, the base station cannot perform diversityreception using the signals received from the respective antennas.Consequently, it is difficult for a base station to obtain a betterreceived signal with decreased fading effects.

[0009] In order to prevent this kind of problem, a base station needonly be provided with the number of AAAs necessary for diversity.However, in this case, the number of antennas to be installed increases,and antenna installation becomes difficult. In addition, as the numberof antennas increases, the number of complex coefficients (receptionweights and transmission weights) to be calculated also increases, andthe scale of computation necessary for weight calculations becomesextremely large.

[0010] Furthermore, when method 2 is used, in directionality for atransmit signal, side lobes are generated in all directions rather thanonly in the desired direction. As a result, a mobile station located ina direction other than the above-mentioned desired direction receivesmajor interference, and consequently has difficulty in achieving goodcommunication. Thus, use of method 2 is not suitable for a multi-userenvironment such as CDMA.

DISCLOSURE OF INVENTION

[0011] It is an object of the present invention to provide a basestation apparatus that suppresses the effects of fading and interferenceand obtains a received signal with good characteristics whilemaintaining good communication quality in a mobile station apparatus(communication terminal apparatus).

[0012] This object can be achieved by providing antenna elements for aplurality of branches arranged so as to have a mutually verticalpositional relationship at a sequence-specific predetermined position inthe horizontal plane on a sequence-by-sequence basis, performingadaptive array antenna processing using a received signal for eachsequence on a branch-by-branch basis, generating a combined signal thatcombines signals resulting from multiplying a received signal for eachabove-mentioned sequence by a sequence-specific weight, and performingdiversity combining using the generated combined signals of each branch.

[0013] Moreover, this object can be achieved by providingvertical-polarization antenna elements corresponding to a first branchand horizontal-polarization antenna elements corresponding to a secondbranch, arranged at mutually predetermined distances atsequence-specific predetermined positions in the horizontal plane,performing adaptive array antenna processing using a received signal foreach sequence on a branch-by-branch basis, generating a combined signalthat combines signals resulting from multiplying a received signal foreach above-mentioned sequence by a sequence-specific weight, andperforming diversity combining using the generated combined signals ofeach branch.

BRIEF DESCRIPTION OF DRAWINGS

[0014]FIG. 1 is a block diagram showing the configuration of a basestation apparatus according to Embodiment 1 of the present invention;

[0015]FIG. 2 is a block diagram showing the configuration of a basestation apparatus according to Embodiment 2 of the present invention;

[0016]FIG. 3 is a block diagram showing the configuration of a basestation apparatus according to Embodiment 3 of the present invention;

[0017]FIG. 4 is a block diagram showing the configuration of a basestation apparatus according to Embodiment 4 of the present invention;

[0018]FIG. 5 is a block diagram showing the configuration of a basestation apparatus according to Embodiment 5 of the present invention;and

[0019]FIG. 6 is a block diagram showing the configuration of a basestation apparatus according to Embodiment 6 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0020] With reference now to the accompanying drawings, embodiments ofthe present invention will be explained in detail below.

[0021] (Embodiment 1)

[0022] A base station provided with an AAA obtains a received signalthat has high gain, and also forms reception directionality (that is,converges the beam width in the horizontal plane), by combining signalsreceived from a plurality of antennas. A base station provided with suchan AAA can increase received signal gain through the introduction of theAAA. That is to say, even if the gain of the signal received by each ofthe antennas forming the AAA is small, this base station can obtain ahigh-gain signal by combining the signals received by the antennas. Withthis base station, therefore, it is possible to reduce the gain of thesignal received by each of the antennas forming the AAA, and thus it ispossible to shorten the length of each antenna.

[0023] Thus, in this embodiment, first, a predetermined antenna sequence(here designated “antenna sequence 1”) is formed by providing antennaelements of shortened length corresponding to the number of branches (inthis embodiment, “branch 1” and “branch 2”), and arranging the antennaelements corresponding to branch 1 (an antenna element group composed ofa plurality of antenna elements) and branch 2 so as to have a mutuallyvertical positional relationship at a predetermined point on thehorizontal plane (here designated “point 1”). Here, it is desirable foreach antenna element to be placed at the above-mentioned predeterminedpoint so that the central axes of the antenna elements corresponding tothe respective branches virtually coincide.

[0024] Next, a predetermined antenna sequence (here designated “antennasequence 2”) formed by means of a similar method is arranged at a pointother than above-mentioned point 1 (here designated “point 2”). Here,the antenna element corresponding to branch 1 (branch 2) in antennasequence 2 is placed at virtually the same height as that at which theantenna element corresponding to branch 1 (branch 2) in antenna sequence1 is placed. Thereafter, the desired number of predetermined antennasequences formed by means of a similar method are arranged. By thismeans, an antenna with a plurality of branches can easily be installed.

[0025] With regard to the length of each antenna element, it is possiblefor this to be set in accordance with the number of sequences, forexample. For example, as the number of sequences increases, the gain ofa signal in which the signals received by the antenna sequences arecombined also increases, and it is therefore possible to shorten thelength of the antenna elements of each sequence.

[0026] An actual example will be described with reference to FIG. 1.FIG. 1 is a block diagram showing the configuration of a base stationapparatus according to Embodiment 1 of the present invention. In thisembodiment, a case will be described, as an example, in which the numberof branches is 2 and the number of sequences is 3.

[0027] First, antenna elements of shortened length (for example, antennaelements of virtually cylindrical shape-though antenna elements of otherthan virtually cylindrical shape are possible) 101-1 and 102-1 areprovided. Antenna element 101-1 (that is, the antenna elementcorresponding to branch 1) and antenna element 102-1 (that is, theantenna element corresponding to branch 2) are arranged so as to have amutually vertical positional relationship at point 1 in the horizontalplane. Here, antenna element 101-1 and antenna element 102-1 arearranged so that their central axes virtually coincide. By this means,antenna sequence 1 is formed. Furthermore, in this embodiment, antennasequence 1 is covered by a radome (for example, a radome of virtuallycylindrical shape) 103-1. This radome 103-1 is used to prevent antennaelement 101-1 and antenna element 102-1 from being affected by wind.

[0028] Next, antenna element 101-2 and antenna element 102-2, having asimilar configuration to antenna element 101-1 and antenna element102-1, are provided. Antenna element 101-2 (that is, the antenna elementcorresponding to branch 1) and antenna element 102-2 (that is, theantenna element corresponding to branch 2) are arranged so as to have amutually vertical positional relationship at point 2 in the horizontalplane. Here, antenna element 101-2 (antenna element 102-2) is placed atvirtually the same height as that at which antenna element 101-1(antenna element 102-1) is placed. By this means, antenna sequence 2 isformed. Antenna sequence 1 is covered by a radome (here, radome 103-2)in the same way as antenna sequence 1.

[0029] Similarly, antenna sequence 3 is formed, by means of the samemethod as described above, using antenna element 101-3 (that is, anantenna element corresponding to branch 1) and antenna element 102-3(that is, an antenna element corresponding to branch 2). It goes withoutsaying that antenna element 101-3 (antenna element 102-3) is placed atvirtually the same height as that at which antenna element 101-1 andantenna element 101-2 (antenna element 102-1 and antenna element 102-2)are placed.

[0030] The overall configuration of a base station apparatus accordingto this embodiment will now be described, again with reference toFIG. 1. In branch 1, the signal received by antenna element 101-1 inantenna sequence 1 (sequence 1 received signal), the signal received byantenna element 101-2 in antenna sequence 2 (sequence 2 receivedsignal), and the signal received by antenna element 101-3 in antennasequence 3 (sequence 3 received signal), are output to a receiving RFsection 104.

[0031] The receiving RF section 104 performs predetermined receptionprocessing, such as frequency conversion, on the sequence 1 receivedsignal through sequence 3 received signal. Following this receptionprocessing, the sequence 1 through sequence 3 received signals areoutput to a received signal processing section 105.

[0032] In the received signal processing section 105, a reception weightcombining section 106 generates a combined signal by multiplying thesequence 1 through sequence 3 received signals that have undergonereception processing by sequence-specific reception weights from aweight update section 107. The generated combined signal is output tothe weight update section 107 and a diversity combining section 108.Using a reference signal, the sequence 1 through sequence 3 receivedsignals that have undergone reception processing from the receiving RFsection 104, and the combined signal from the reception weight combiningsection 106, the weight update section 107 generates reception weightsspecific to sequence 1 through sequence 3, respectively. The generatedreception weights are output to the reception weight combining section106 and a transmission weight combining section 113.

[0033] The transmission weight combining section 113 uses the receptionweights specific to sequence 1 through sequence 3, respectively, fromthe weight update section 107 as transmission weights specific tosequence 1 through sequence 3, respectively. That is to say, thetransmission weight combining section 113 generates sequence 1 throughsequence 3 transmit signals by multiplying a transmit signal bytransmission weights specific to sequence 1 through sequence 3,respectively, and outputs these transmit signals to a transmitting RFsection 114.

[0034] The transmitting RF section 114 performs predeterminedtransmission processing, such as frequency conversion, on the sequence 1through sequence 3 transmit signals, and transmits the sequence 1through sequence 3 transmit signals that have undergone transmissionprocessing via sequence 1 antenna element 101-1 through sequence 3antenna element 101-3, respectively.

[0035] Meanwhile, in branch 2, the signal received by antenna element102-1 in antenna sequence 1 (sequence 1 received signal), the signalreceived by antenna element 102-2 in antenna sequence 2 (sequence 2received signal), and the signal received by antenna element 102-3 inantenna sequence 3 (sequence 3 received signal), are output to areceiving RF section 109.

[0036] Receiving RF section 109 performs predetermined receptionprocessing, such as frequency conversion, on the sequence 1 receivedsignal through sequence 3 received signal. Following this receptionprocessing, the sequence 1 through sequence 3 received signals areoutput to a received signal processing section 110.

[0037] In received signal processing section 110, a reception weightcombining section 111 generates a combined signal by multiplying thesequence 1 through sequence 3 received signals that have undergonereception processing by sequence-specific reception weights from aweight update section 112. The generated combined signal is output toweight update section 112 and the diversity combining section 108. Usinga reference signal, the sequence 1 through sequence 3 received signalsthat have undergone reception processing from receiving RF section 109,and the combined signal from reception weight combining section 111,weight update section 112 generates reception weights specific tosequence 1 through sequence 3, respectively. The generated receptionweights are output to reception weight combining section 111.

[0038] The diversity combining section 108 generates a new receivedsignal by performing diversity combining using the combined signalgenerated by reception weight combining section 106 and the combinedsignal generated by reception weight combining section 111.

[0039] The operation of a base station apparatus that has the aboveconfiguration will now be described, again with reference to FIG. 1. Inorder to simplify the description, it is here assumed that theaforementioned base station apparatus performs communication with mobilestation apparatus 1. Mobile station apparatus 1 transmits an informationsignal (containing a known signal) and a reference signal at differenttimes.

[0040] A signal transmitted by mobile station apparatus 1 is received bya base station apparatus according to this embodiment via sequence 1through sequence 3 antennas. First, in branch 1, signals received bysequence 1 antenna element 101-1 through sequence 3 antenna element101-3-that is, sequence 1 through sequence 3 received signals-aresubjected to predetermined reception processing, such as frequencyconversion, by receiving RF section 104, and are then output to receivedsignal processing section 105. In received signal processing section105, the kind of adaptive array antenna processing (hereinafter referredto as “AAA processing”) described below is performed.

[0041] At the reception time for a reference signal (that is, when thesequence 1 through sequence 3 received signals are signals correspondingto a reference signal), in reception weight combining section 106,sequence 1 through sequence 3 received signals that have undergonereception processing are each multiplied by the respectivesequence-specific reception weight from weight update section 107, andthe sequence 1 through sequence 3 received signals multiplied by thesequence-specific reception weights are combined. By this means, acombined signal is generated. The generated combined signal is output toweight update section 107. In weight update section 107, the receptionweights specific to sequence 1 through sequence 3, respectively, areupdated so that the difference between the combined signal and apreviously stored reference signal is made smaller. The updatedreception weights are output to reception weight combining section 106and the transmission weight combining section 113.

[0042] At the reception time for an information signal (containing aknown signal) (that is, when the sequence 1 through sequence 3 receivedsignals are signals corresponding to an information signal), inreception weight combining section 106, sequence 1 through sequence 3received signals multiplied by sequence-specific reception weights arecombined. By this means, a branch 1 combined signal is generated. Thisbranch 1 combined signal is a signal that has a large array gain. As aresult, interference waves (such as adjacent-channel interference waves,same-channel interference waves, and delayed waves, for example) aresuppressed in this branch 1 combined signal. The generated branch 1combined signal is output to the diversity combining section 108.

[0043] Next, in branch 2, signals received by sequence 1 antenna element102-1 through sequence 3 antenna element 102-3—that is, sequence 1through sequence 3 received signals—are output to received signalprocessing section 109. In received signal processing section 109,reception weight combining section 111, and weight update section 112,the same kind of processing is performed as in receiving RF section 104,reception weight combining section 106, and weight update section 107,respectively, for branch 1. As a result, sequence 1 through sequence 3received signals multiplied by sequence-specific reception weights arecombined in reception weight combining section 111. By this means, abranch 2 combined signal is generated. This branch 2 combined signal isa signal that has a large array gain. As a result, interference waves(such as adjacent-channel interference waves, same-channel interferencewaves, and delayed waves, for example) are suppressed in this branch 2combined signal. The generated branch 2 combined signal is output to thediversity-combining section 108.

[0044] In the diversity combining section 108, diversity combining isperformed using the branch 1 combined signal from reception weightcombining section 106 and the branch 2 combined signal from receptionweight combining section 111.

[0045] That is to say, channel estimation—that is, fading fluctuationestimation—for branch 1 (branch 2) is first carried out using the signalcorresponding to a known signal in the branch 1 (branch 2) combinedsignal. By this means, a branch 1 channel estimate (α1) and branch 2channel estimate (α2) are generated. Then diversity combining isperformed using the signal corresponding to an information signal in thebranch 1 combined signal (r1(t)), the signal corresponding to aninformation signal in the branch 2 combined signal (r2(t)), the branch 1channel estimate, and the branch 2 channel estimate. By this means, anew received signal is generated.

[0046] Specifically, when maximal-ratio combining is used for diversitycombining, for example, the new received signal (r(t)) is expressed bythe equation shown below. Below, α1* indicates the complex conjugate ofα1, and α2* indicates the complex conjugate of α2.

r(t)=α1*(t)r 1(t)+α2*(t)r 2(t)  (1)

[0047] When equal-gain combining is used for diversity combining, thenew received signal is expressed by the equation shown below.

r(t)=α1*(t)r 1(t)/|α1|+α2*(t)r 2(t)/|α2|  (2)

[0048] When selective combining is used for diversity combining, the newreceived signal is expressed by the equations shown below.

r(t)=α1*(t)r 1(t)/|α1| (where |α1|>|α2|)  (3)

r(t)=α2*(t)r 2(t)/|α2| (where |α1|<|α2|)  (4)

[0049] It is possible to use any one of maximal-ratio combining,equal-gain combining, or selective combining for diversity combining.The received signal with the best characteristics can be obtained byusing maximal-ratio combining.

[0050] In the obtained new received signal, the effects of fadingfluctuation are lessened due to the fact that diversity combining hasbeen performed.

[0051] Meanwhile, a transmit signal is output to the transmission weightcombining section 113. In the transmission weight combining section 113,sequence 1 through sequence 3 transmit signals are generated bymultiplying the transmit signal by transmission weights specific tosequence 1 through sequence 3, respectively. Transmission weightsspecific to sequence 1 through sequence 3, respectively, are equivalentto the reception weights specific to sequence 1 through sequence 3,respectively, updated by weight update section 107. The generatedsequence 1 through sequence 3 transmit signals are output to thetransmitting RF section 114.

[0052] After undergoing predetermined transmission processing by thetransmitting RF section 114, the sequence 1 through sequence 3 transmitsignals are transmitted to receiving station apparatus 1 via sequence 1antenna element 101-1 through sequence 3 antenna element 101-3 in branch1, respectively.

[0053] In the directionalities of signals transmitted via sequence 1antenna element 101-1 through sequence 3 antenna element 101-3, a beamis present in the direction of arrival of mobile station apparatus 1 dueto the fact that multiplication by transmission weights has beenperformed by the transmission weight combining section 113. As a result,reception power can be increased in mobile station apparatus 1, andinterference imposed on mobile station apparatuses other than mobilestation apparatus 1 can be suppressed. Therefore, communication qualitycan be maintained at a good level in mobile station apparatus 1 andother mobile station apparatuses.

[0054] In this embodiment, a case has been described in which transmitsignals are transmitted from branch 1, but it is also possible to fortransmit signals to be transmitted from branch 2. However, the branch 1antenna (that is, antenna element 101-1 through antenna element 101-3)is arranged at a higher position than the branch 2 antenna (that is,antenna element 102-1 through antenna element 102-3). Thus, transmissionof transmit signals from branch 1 is advantageous in terms ofpropagation loss and securement of line-of-sight. It is thereforepreferable for transmit signals to be transmitted from branch 1 ratherthan branch 2.

[0055] As described above, in this embodiment, a plurality of antennaelements are arranged so as to have a mutually vertical positionalrelationship at a predetermined point in the horizontal plane on asequence-by-sequence basis. By this means, a plurality of antennaelement branches can easily be installed. Also, a signal in whichinterference waves are suppressed can be obtained by multiplying thereceived signal of each sequence by a sequence-specific receptionweight, on a branch-by-branch basis, and combining the received signalsof the respective sequences that have been multiplied by a receptionweight (performing AAA processing). By this means, it is possible toextract only the signal transmitted by the desired mobile stationapparatus from a received signal. Moreover, by performing diversitycombining of combined signals obtained by AAA processing on abranch-by-branch basis, it is possible to obtain a signal in which theeffects of fading fluctuation are lessened.

[0056] (Embodiment 2)

[0057] In this embodiment, a case is described, with reference to FIG.2, in which the amount of reception weight computation in AAA processingin Embodiment 1 is reduced. FIG. 2 is a block diagram showing theconfiguration of a base station apparatus according to Embodiment 2 ofthe present invention. Parts in FIG. 2 identical to those in Embodiment1 (FIG. 1) are assigned the same codes as in FIG. 1 and their detailedexplanations are omitted.

[0058] In FIG. 2, a base station apparatus according to this embodimenthas a configuration wherein weight update section 112 is eliminated froma base station apparatus according to Embodiment 1, and a receptionweight combining section 201 is provided instead of reception weightcombining section 111.

[0059] To consider a predetermined sequence (here, for example, sequence1), a signal received by branch 1 antenna element 101-1 and a signalreceived by branch 2 antenna element 102-1 virtually coincide as regardsdirection of arrival, and differ only in signal strength. The same alsoapplies to sequence 2 and sequence 3.

[0060] Thus, in this embodiment, reception weight calculation isperformed for only one of a plurality of branches, and the calculatedreception weights are used as reception weights for all theabove-mentioned plurality of branches. Following this, diversitycombining that takes account of the effects of fading fluctuation isperformed using the combined signal obtained by AAA processing in theabove-mentioned plurality of branches. Thus, reception weightcalculation is performed for only one branch rather than for allbranches, enabling the amount of computation required for receptionweight calculation to be reduced.

[0061] At the reception time for an information signal (containing aknown signal) (that is, when the sequence 1 through sequence 3 receivedsignals are signals corresponding to an information signal), inreception weight combining section 201, sequence 1 through sequence 3received signals that have undergone reception processing are multipliedby sequence-specific reception weights from weight update section 107,respectively, and the sequence 1 through sequence 3 received signalsmultiplied by the sequence-specific reception weights are combined. Bythis means, a branch 2 combined signal is generated.

[0062] As described above, in this embodiment, reception weightcalculation is performed for only one of a plurality of branches, andthe calculated reception weights are used as reception weights for allthe above-mentioned plurality of branches. By this means, it is possibleto reduce the amount of computation required for reception weightcalculation compared with Embodiment 1.

[0063] (Embodiment 3)

[0064] In this embodiment, a case is described, with reference to FIG.3, in which diversity transmission is performed in Embodiment 2. FIG. 3is a block diagram showing the configuration of a base station apparatusaccording to Embodiment 3 of the present invention. Parts in FIG. 3identical to those in Embodiment 2 (FIG. 2) are assigned the same codesas in FIG. 2 and their detailed explanations are omitted.

[0065] In FIG. 3, a base station apparatus according to this embodimenthas a configuration wherein a transmitting antenna selecting section301, selecting section 302, and transmitting RF section 303 are providedin a base station apparatus according to Embodiment 1.

[0066] As described in Embodiment 2 above, to consider a predeterminedsequence (here, for example, sequence 1), a signal received by branch 1antenna element 101-1 and a signal received by branch 2 antenna element102-1 virtually coincide as regards direction of arrival, and differonly in signal strength.

[0067] Thus, in this embodiment, reception weight calculation isperformed for only one of a plurality of branches, and the calculatedreception weights are used as reception weights and transmission weightsfor all the above-mentioned plurality of branches. Following this,diversity combining that takes account of the effects of fadingfluctuation is performed using the combined signal obtained by AAAprocessing in the above-mentioned plurality of branches. Thus,transmission weight calculation is performed for only one branch ratherthan for all branches, enabling the amount of computation required fortransmission weight calculation to be reduced.

[0068] The transmitting antenna selecting section 301 measures thereception power of a branch 1 combined signal generated by a receptionweight combining section 106 and the reception power of a branch 2combined signal generated by a reception weight combining section 201,and selects the branch corresponding to the combined signal with thegreater reception power as the branch to transmit a transmit signal.This transmitting antenna selecting section 301 outputs the selectionresult to the selecting section 302.

[0069] The selecting section 302 outputs sequence 1 through sequence 3transmit signals from a transmission weight combining section 113 to atransmitting RF section 114 or transmitting RF section 303 in accordancewith the selection result of the transmitting antenna selecting section301. That is to say, when branch 1 (branch 2) is selected by thetransmitting antenna selecting section 301, the selecting section 302outputs sequence 1 through sequence 3 transmit signals to transmittingRF section 114 (transmitting RF section 303).

[0070] The transmitting RF section 303 has an identical configuration toabove-described transmitting RF section 114, and performs predeterminedtransmission processing, such as frequency conversion, on sequence 1through sequence 3 transmit signals, and then transmits sequence 1through sequence 3 transmit signals that have undergone transmissionprocessing via sequence 1 antenna element 102-1 through sequence 3antenna element 102-3, respectively.

[0071] In the directionalities of signals transmitted via sequence 1antenna element 101-1 through sequence 3 antenna element 101-3 (whenbranch 1 is selected) or sequence 1 antenna element 102-1 throughsequence 3 antenna element 102-3 (when branch 2 is selected), a beam ispresent in the direction of arrival of mobile station apparatus 1 due tothe fact that multiplication by transmission weights has been performedby the transmission weight combining section 113. As a result, receptionpower can be increased in mobile station apparatus 1, and interferenceimposed on mobile station apparatuses other than mobile stationapparatus 1 can be suppressed. Therefore, communication quality can bemaintained at a good level in mobile station apparatus 1 and othermobile station apparatuses.

[0072] Furthermore, by performing transmission to mobile stationapparatus l via a branch selected based on the reception power of thecombined signal of each branch (that is, diversity transmission), it ispossible to compensate for a drop in reception power due to fadingfluctuation in mobile station apparatus 1

[0073] As described above, in this embodiment, reception weightcalculation is performed for only one of a plurality of branches, andthe calculated reception weights are used as reception weights andtransmission weights for all the above-mentioned plurality of branches.By this means, it is possible to reduce the amount of computationrequired for transmission weight calculation, and also perform diversitytransmission.

[0074] (Embodiment 4)

[0075] In this embodiment, a case is described in which polarizationdiversity is used in Embodiment 1.

[0076] In mobile communications, a mobile station apparatus user usesthat mobile station apparatus for communication inclined at an angle of45 degrees to the horizontal. Consequently, a vertically polarized waveand a horizontally polarized wave arrive at a base station apparatus. Asthe fading correlation between a vertically polarized wave andhorizontally polarized wave is very low, the application of polarizationdiversity using a vertically polarized wave and horizontally polarizedwave enables a signal with greater gain to be obtained than in the caseof space diversity, in which a plurality of antennas are used in aspatially separated arrangement.

[0077] Thus, in this embodiment, polarization diversity is applied.However, if a single antenna is formed by leaving a predetermineddistance between an antenna element that transmits and receives avertically polarized wave (hereinafter referred to as “verticalpolarization antenna element”) and an antenna element that transmits andreceives a horizontally polarized wave (hereinafter referred to as“horizontal polarization antenna element”), the thickness of the formedantenna will exceed 0.5 received signal wavelength. As a result, sidelobes are generated in the directionality of a signal transmitted bythis formed antenna. Consequently, a vertical polarization antennaelement and horizontal polarization antenna element cannot be applied toan AAA.

[0078] In this embodiment, therefore, in order to reduce the thicknessof the formed antenna, an antenna element that has a large beam width(preferably on the order of 120 degrees) in directionality is used as avertical polarization antenna element and a horizontal polarizationantenna element. Using an antenna element with such a beam width rendersa large reflector plate unnecessary, enabling the thickness of theformed antenna to be reduced. Even if an antenna element with a largebeam width in directionality is used here, a base station equipped withan AAA formed by using a plurality of such antenna elements can narrowthe beam width in directionality.

[0079] An actual example will now be described with reference to FIG. 4.FIG. 4 is a block diagram showing the configuration of a base stationapparatus according to Embodiment 4 of the present invention. Parts inFIG. 4 identical to those in Embodiment 1 (FIG. 1) are assigned the samecodes as in FIG. 1 and their detailed explanations are omitted. In thisembodiment, a case will be described, as an example, in which the numberof branches is 2 and the number of sequences is 3.

[0080] First, a vertical polarization antenna element 401-1 andhorizontal polarization antenna element 402-1 (for example, antennaelements of virtually cylindrical shape) are provided. Each antennaelement has a large beam width (preferably on the order of 120 degrees)in directionality.

[0081] A predetermined antenna sequence (here designated “antennasequence 1”) is formed by arranging vertical polarization antennaelement 401-1 and horizontal polarization antenna element 402-1 with apredetermined distance left between them at a predetermined point on thehorizontal plane (here designated “point 1”). In FIG. 4, an example isshown in which vertical polarization antenna element 401-1 andhorizontal polarization antenna element 402-1 are arranged virtually inparallel, but there are no restrictions on the positional relationshipbetween antennas.

[0082] Furthermore, in this embodiment, antenna sequence 1 is covered bya radome 403-1. This radome 403-1 has the same kind of configuration asradome 103-1 in Embodiment 1. In order to prevent the generation of sidelobes in the directionality of a signal transmitted by this antennasequence 1, the diameter of radome 403-1 is determined based on thedirectionality of vertical polarization antenna element 401-1 andhorizontal polarization antenna element 402-1 so that the diameter ofradome 403-1 is 0.5 received signal wavelength.

[0083] Next, a vertical polarization antenna element 401-2 (horizontalpolarization antenna element 402-2) that has the same kind ofconfiguration as vertical polarization antenna element 401-1 (horizontalpolarization antenna element 402-1) is provided. A predetermined antennasequence (here designated “antenna sequence 2”) is formed by arrangingvertical polarization antenna element 401-2 and horizontal polarizationantenna element 402-2 with a predetermined distance left between them ata predetermined point other than point 1 on the horizontal plane (heredesignated “point 2”). In FIG. 4, an example is shown in which verticalpolarization antenna element 401-1 and horizontal polarization antennaelement 402-1 are arranged virtually in parallel, but there are norestrictions on the positional relationship between antennas. By thismeans, antenna sequence 2 is formed. This antenna sequence 2 is coveredby a radome (here, radome 403-2), in the same way as antenna sequence 1.

[0084] Similarly, antenna sequence 3 is formed, by means of the samemethod as described above, using vertical polarization antenna element401-3 and horizontal polarization antenna element 402-3.

[0085] The overall configuration of a base station apparatus accordingto this embodiment will now be described, again with reference to FIG.4. In branch 1, the signal received by vertical polarization antennaelement 401-1 in antenna sequence 1 (sequence 1 received signal), thesignal received by vertical polarization antenna element 401-2 inantenna sequence 2 (sequence 2 received signal), and the signal receivedby vertical polarization antenna element 401-3 in antenna sequence 3(sequence 3 received signal), are output to a receiving RF section 104.The same kind of processing is then performed by receiving RF section104, reception weight combining section 106, and weight update section107 as described in Embodiment 1. As a result, a branch 1 combinedsignal is generated by reception weight combining section 106.Interference waves (such as adjacent-channel interference waves,same-channel interference waves, and delayed waves, for example) aresuppressed in this branch 1 combined signal. The generated branch 1combined signal is output to a diversity combining section 108.

[0086] Next, in branch 2, the signal received by horizontal polarizationantenna element 402-1 in antenna sequence 1 (sequence 1 receivedsignal), the signal received by horizontal polarization antenna element402-2 in antenna sequence 2 (sequence 2 received signal), and the signalreceived by horizontal polarization antenna element 402-3 in antennasequence 3 (sequence 3 received signal), are output to a receiving RFsection 109. The same kind of processing is then performed by receivingRF section 109, reception weight combining section 111, and weightupdate section 112 as described in Embodiment 1. As a result, a branch 2combined signal is generated by reception weight combining section 111.Interference waves (such as adjacent-channel interference waves,same-channel interference waves, and delayed waves, for example) aresuppressed in this branch 2 combined signal. The generated branch 2combined signal is output to the diversity combining section 108.

[0087] In the diversity combining section 108, the same kind ofprocessing is performed as described in Embodiment 1. By this means, anew received signal is generated. In the obtained new received signal,the effects of fading fluctuation are lessened due to the fact thatdiversity combining has been performed.

[0088] Meanwhile, sequence 1 through sequence 3 transmit signalsgenerated by the transmission weight combining section 113 are subjectedto transmission processing by receiving RF section 104, and are thentransmitted to receiving station apparatus 1 via vertical polarizationantenna element 401-1 through vertical polarization antenna element401-3, respectively.

[0089] Antenna elements with a large beam width in directionality areused as vertical polarization antenna elements 401-1 through 401-3 andhorizontal polarization antenna elements 402-1 through 402-3, but a basestation apparatus that has such a plurality of vertical polarizationantenna elements and horizontal polarization antenna elements can narrowthe beam width in directionality.

[0090] As described above, in this embodiment, a vertical polarizationantenna element and horizontal polarization antenna element that have alarge beam width in directionality are arranged at a predetermineddistance on a sequence-by-sequence basis. By this means, the thicknessof antennas formed on a sequence-by-sequence basis can be reduced, andthus the generation of side lobes in the directionality of signalstransmitted by these antennas can be prevented, and the arrangement ofthese antennas can be performed easily. Also, a signal in whichinterference waves are suppressed can be obtained by multiplying thereceived signal of each sequence by a sequence-specific receptionweight, on a branch-by-branch basis, and combining the received signalsof the respective sequences that have been multiplied by a receptionweight (performing AAA processing). By this means, it is possible toextract only the signal transmitted by the desired mobile stationapparatus from a received signal. Moreover, by performing diversitycombining of combined signals obtained by AAA processing on abranch-by-branch basis, it is possible to obtain a signal in which theeffects of fading fluctuation are lessened.

[0091] (Embodiment 5)

[0092] In this embodiment, a case is described, with reference to FIG.5, in which the amount of reception weight computation in AAA processingin Embodiment 4 is reduced. FIG. 5 is a block diagram showing theconfiguration of a base station apparatus according to Embodiment 5 ofthe present invention. Parts in FIG. 5 identical to those in Embodiment4 (FIG. 4) are assigned the same codes as in FIG. 4 and their detailedexplanations are omitted.

[0093] In FIG. 5, a base station apparatus according to this embodimenthas a configuration wherein weight update section 112 is eliminated froma base station apparatus according to Embodiment 4, and a receptionweight combining section 201 is provided instead of reception weightcombining section 111.

[0094] To consider a predetermined sequence (here, for example, sequence1), the installation position of branch 1 vertical polarization antennaelement 401-1 with respect to mobile station apparatus 1 and theinstallation position of branch 2 horizontal polarization antennaelement 402-1 with respect to mobile station apparatus 1 are virtuallythe same. As a result, a signal received by vertical polarizationantenna element 401-1 and a signal received by horizontal polarizationantenna element 402-1 virtually coincide as regards direction ofarrival, and differ only in signal strength. The same also applies tosequence 2 and sequence 3.

[0095] Thus, in this embodiment, reception weight calculation isperformed for only one of a plurality of branches, and the calculatedreception weights are used as reception weights for all theabove-mentioned plurality of branches. Following this, diversitycombining that takes account of the effects of fading fluctuation isperformed using the combined signal obtained by AAA processing in theabove-mentioned plurality of branches. Thus, reception weightcalculation is performed for only one branch rather than for allbranches, enabling the amount of computation required for receptionweight calculation to be reduced.

[0096] At the reception time for an information signal (containing aknown signal) (that is, when the sequence 1 through sequence 3 receivedsignals are signals corresponding to an information signal), inreception weight combining section 201, sequence 1 through sequence 3received signals that have undergone reception processing are multipliedsequence-specific reception weights from a weight update section 107,respectively, and the sequence 1 through sequence 3 received signalsmultiplied by the sequence-specific reception weights are combined. Bythis means, a branch 2 combined signal is generated.

[0097] As described above, reception weight calculation is performed foronly one of a plurality of branches, and the calculated receptionweights are used as reception weights for all the above-mentionedplurality of branches. By this means, it is possible to reduce theamount of computation required for reception weight calculation comparedwith Embodiment 4.

[0098] (Embodiment 6)

[0099] In this embodiment, a case is described, with reference to FIG.6, in which diversity transmission is performed in Embodiment 5. FIG. 6is a block diagram showing the configuration of a base station apparatusaccording to Embodiment 6 of the present invention. Parts in FIG. 6identical to those in Embodiment 4 (FIG. 4) are assigned the same codesas in FIG. 4 and their detailed explanations are omitted.

[0100] In FIG. 6, a base station apparatus according to this embodimenthas a configuration wherein a transmitting antenna selecting section301, selecting section 302, and transmitting RF section 303 are providedin a base station apparatus according to Embodiment 5.

[0101] As described in Embodiment 5 above, to consider a predeterminedsequence (here, for example, sequence 1) the installation position ofbranch 1 vertical polarization antenna element 401-1 with respect tomobile station apparatus 1 and the installation position of branch 2horizontal polarization antenna element 402-1 with respect to mobilestation apparatus 1 are virtually the same. As a result, a signalreceived by vertical polarization antenna element 401-1 and a signalreceived by horizontal polarization antenna element 402-1 virtuallycoincide as regards direction of arrival, and differ only in signalstrength. The same also applies to sequence 2 and sequence 3.

[0102] Thus, in this embodiment, the transmitting antenna selectingsection 301 measures the reception power of a branch 1 combined signalgenerated by a reception weight combining section 106 and the receptionpower of a branch 2 combined signal generated by a reception weightcombining section 201, and selects the branch corresponding to thecombined signal with the greater reception power as the branch totransmit a transmit signal. This transmitting antenna selecting section301 outputs the selection result to the selecting section 302.

[0103] The selecting section 302 outputs sequence 1 through sequence 3transmit signals from a transmission weight combining section 113 to atransmitting RF section 114 or transmitting RF section 303 in accordancewith the selection result of the transmitting antenna selecting section301. That is to say, when the vertical polarization antenna (horizontalpolarization antenna) is selected by the transmitting antenna selectingsection 301, the selecting section 302 outputs sequence 1 throughsequence 3 transmit signals to transmitting RF section 114 (transmittingRF section 303).

[0104] In the directionalities of signals transmitted via sequence 1antenna element 401-1 through sequence 3 antenna element 401-3 (when thevertical polarization antenna is selected) or sequence 1 antenna element402-1 through sequence 3 antenna element 402-3 (when the horizontalpolarization antenna is selected), a beam is present in the direction ofarrival of mobile station apparatus 1 due to the fact thatmultiplication by transmission weights has been performed by thetransmission weight combining section 113. As a result, reception powercan be increased in mobile station apparatus 1, and interference imposedon mobile station apparatuses other than mobile station apparatus 1 canbe suppressed. Therefore, communication quality can be maintained at agood level in mobile station apparatus 1 and other mobile stationapparatuses.

[0105] Furthermore, by performing transmission to mobile stationapparatus 1 via a branch selected based on the reception power of thecombined signal of each branch (that is, diversity transmission), it ispossible to compensate for a drop in reception power due to fadingfluctuation in mobile station apparatus 1.

[0106] As described above, in this embodiment, reception weightcalculation is performed for only one of a plurality of branches, andthe calculated reception weights are used as reception weights andtransmission weights for all the above-mentioned plurality of branches.By this means, it is possible to reduce the amount of computationrequired for transmission weight calculation, and also perform diversitytransmission.

[0107] As described above, according to the present invention, it ispossible to provide a base station apparatus that suppresses the effectsof fading and interference and obtains a received signal with goodcharacteristics while maintaining good communication quality in a mobilestation apparatus.

[0108] This application is based on Japanese Patent Application No.2000-389528 filed on Dec. 21, 2000, entire contents of which areexpressly incorporated by reference herein.

[0109] Industrial Applicability

[0110] The present invention relates to a base station apparatus used ina digital mobile communication system, and is particularly suitable foruse in a base station apparatus provided with an adaptive array antenna.

1. A base station apparatus comprising: a plurality of antenna elementgroups composed of a plurality of antenna elements and arranged in avertical direction; a reception weight combining section that performsmultiplication by a weight and combining for each received signalreceived by said antenna element of said antenna element group; and adiversity combining section that performs diversity combining of areceived signal of each said antenna group combined by said receptionweight combining section.
 2. The base station apparatus according toclaim 1, wherein said reception weight combining section uses a commonweight in said antenna element group.
 3. The base station apparatusaccording to claim 1, further comprising: a calculating section thatcalculates reception power of said reception weight combining section; aselecting section that selects said antenna element group based onreception power calculated by said calculating section; a transmissionweight combining section that performs multiplication by a weight usedby said reception weight combining section of said antenna element groupselected by said selecting section for each transmit signal; and adiversity transmission section that transmits a transmit signal combinedby said transmission weight combining section from said antenna elementgroup selected by said selecting section.
 4. A base station apparatuscomprising: a first antenna element group composed of a plurality ofvertical polarization antenna elements; a second antenna element groupcomposed of a plurality of horizontal polarization antenna elements; areception weight combining section that performs multiplication by aweight for each received signal of said vertical polarization antennaelement of said first antenna element group and said horizontalpolarization antenna element of said second antenna element group, andcombines an obtained received signal for each said first antenna elementgroup or said second antenna element group; and a diversity combiningsection that performs diversity combining of a received signal of saidfirst antenna element group and said second antenna element groupcombined by said reception weight combining section.
 5. The base stationapparatus according to claim 4, wherein said reception weight combiningsection uses a common weight in said first antenna element group andsaid second antenna element group.
 6. The base station apparatusaccording to claim 4, further comprising: a calculating section thatcalculates reception power of said reception weight combining section; aselecting section that selects one or other of said first antennaelement group or said second antenna element group based on receptionpower calculated by said calculating section; a transmission weightcombining section that performs multiplication by a weight used by saidreception weight combining section of said antenna element groupselected by said selecting section for each transmit signal; and adiversity transmission section that transmits a transmit signal combinedby said transmission weight combining section from an antenna elementgroup selected by said selecting section.
 7. A communication terminalapparatus that performs radio communication with the base stationapparatus according to claim 1.